Vertical P-trap alternative to stop sewer gas smells

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Jakedeg

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Hi All!

I moved into a new home last fall. It was fully gut-renovated back in 2014 and from the outer looks of everything, they spared no expense and did a great job. A few months into living here, I decided the walk-in shower drain was a bit slow, so I snaked it. I got a ton of stinky gunk out of there and I was thrilled. The drain was fast again, and I assumed after a few minutes, the smell would clear. Unfortunately, it did not. Ever since then, I have sewer gas smell. It goes away when I run the shower for a few minutes, but comes back soon after I turn the shower off. When I look down the drain, I can see standing water about 8" down, but I assume that there must be a partial p-trap there but maybe it's not deep enough to allow the water to make a complete seal and some air can travel freely above the water line.And I figure the hair and gunk I pulled out of the drain was actually blocking some of the gas from making its way into the bathroom... Does this sound like a plausible theory?

So now I'm trying to figure out what to do. I have been looking at back-flow preventer devices on Amazon and I've bought and tried this one and this one but both make the drain way too slow so I'm standing in water after a few seconds. Does anyone have a recommendation for a device like this that actually can keep up with a shower running full-force?

After more research, I found this YouTube video where he basically makes a DIY P-trap alternative by having a vertical pipe (in red) with the bottom submerged in a cup (in green) which fills with water (in blue). Like this:

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It seems like such a good idea that I should be able to buy something like this that just fits right into my 2" ID pipe. Does this sort of thing exist off-the-shelf? Does it have a name? If not, is there any reason I shouldn't try to make one myself out of PVC? Will it be just as slow as the things I've tried on Amazon?
 

Reach4

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What you propose is a little like a bell trap but not quite. I made my own similar trap to yours, and the part you did in green was a cut-off aluminum V-8 can IIRC.
 

breplum

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Aside from scum in the vertical pipe portion before the p-trap, there should be no smell from the trap. Use a toilet brush or jumbo bottle brush to clean the vertical pipe below the grate.
If you still have odor, frankly, if you can, I would have a pressurized smoke test done on the drainage.
The water seal of a p-trap is specifically designed to completely and successfully prevent odors.
I do have a neighbor who complains about odor in her bathroom and we've never been able to pinpoint the smell.
 

James Henry

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pour some bleach around and down the drain. if all you smell is bleach after 10 or 20 minutes then you just have a sensitive nose.
 

Jakedeg

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Aside from scum in the vertical pipe portion before the p-trap, there should be no smell from the trap. Use a toilet brush or jumbo bottle brush to clean the vertical pipe below the grate.
If you still have odor, frankly, if you can, I would have a pressurized smoke test done on the drainage.
The water seal of a p-trap is specifically designed to completely and successfully prevent odors.
I do have a neighbor who complains about odor in her bathroom and we've never been able to pinpoint the smell.
Yeah. Thanks. I cleaned the vertical drop-down pipe as much as I could, including a brush attachment on a screw gun. That didn't make a difference. Plus, we didn't smell anything until after I snaked the drain the first time, and the gunk came up from well below the p-trap. So I don't think the smell is from the vertical drop-down.
pour some bleach around and down the drain. if all you smell is bleach after 10 or 20 minutes then you just have a sensitive nose.
I also poured a lot of bleach down there. We could only smell strong bleach for about 3 days but after that, the bleach smell faded and the sewer smell came back.

My theory is that the current p-trap isn't installed or configured correctly to it's not making a full water seal. Like, the water level is below the top of the trap and some gas can get through. Kind of like this;

Screen Shot 2022-04-30 at 10.44.25 AM.png


Does that seem possible? I guess i could try to get a mirror or something down there to look...
 
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Possible but unlikely.


If the home was inspected and done with permits, there will be "cleanouts" on that line. Open those up and you may learn more.

Share photos for better advice.
Often even a missing trap is not that stinky, so I think your issue may be elsewhere.

Bleach was never going to work, and drain chemicals won't help either.

Try blocking the drain with plastic or a rubber plug when not in use, to verify the smell is really coming from where you think it's coming from.


Or, hire a pro.
 

Sylvan

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The right way to get rid of crud /soap scum /grease /oils (skin. body, etc) is water Jetting

Water Jetting scours the lines to restore full flow and removes the crud that causes odor

images.jpg
 

John Gayewski

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If there is hair in the trap it could, by way of capillary action, suck the trap down enough to let sewer gas in. The trap needs cleaned. Don't build a contraption. There could be other reasons the trap is being siphoned. It's almost definitely not a trap that's too shallow as they are made and bought from engineered specs.
 
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